Arthur Lute’s arduous journey from his days as a U.S. Marine to his nights sleeping on the streets illustrates the challenge for the Obama administration to fulfill its promise to end homelessness among veterans by 2015. Lute has post-traumatic stress disorder from the 1983 bombing of the Marine barracks in Lebanon. He spent years drifting through jobs, two years in prison for assault, then 15 months sleeping in the bushes outside the police department of this city south of San Diego.